CVE-2026-36798 Overview
CVE-2026-36798 identifies multiple stack overflow vulnerabilities in the Tenda G0 router running firmware version v15.11.0.5. The flaws reside in the formSetDebugCfg function and are reachable through the enable, level, and module parameters. An unauthenticated remote attacker can send a crafted HTTP request to trigger a stack-based buffer overflow [CWE-121]. Successful exploitation causes a Denial of Service (DoS) on the affected device, disrupting network connectivity for downstream clients. The vulnerability requires user interaction according to the CVSS vector but no privileges, making it accessible from any network position that can reach the device's web management interface.
Critical Impact
Unauthenticated attackers can crash the Tenda G0 router via crafted HTTP requests, disrupting network availability for all connected clients.
Affected Products
- Shenzhen Tenda Technology Co., Ltd Tenda G0
- Firmware version v15.11.0.5
- formSetDebugCfg HTTP handler
Discovery Timeline
- 2026-06-09 - CVE-2026-36798 published to NVD
- 2026-06-10 - Last updated in NVD database
Technical Details for CVE-2026-36798
Vulnerability Analysis
The vulnerability affects the formSetDebugCfg request handler in the Tenda G0 web management interface. The handler processes three HTTP parameters: enable, level, and module. Each parameter is copied into a fixed-size stack buffer without proper length validation. When an attacker submits an oversized value for any of these parameters, the copy operation writes past the buffer boundary and corrupts adjacent stack memory, including saved return addresses.
The condition is classified as a stack-based buffer overflow [CWE-121]. Because the device firmware lacks effective stack canaries and address space layout randomization on the target architecture, the corruption reliably crashes the HTTP daemon. The router becomes unresponsive until it is rebooted.
Public proof-of-concept materials are available in the GitHub PoC Repository.
Root Cause
The root cause is the absence of bounds checking on user-controlled input copied into stack buffers within formSetDebugCfg. The handler trusts the length of the enable, level, and module query string values supplied by the HTTP client. Standard unsafe string operations write attacker-controlled data into stack frames sized for short configuration values.
Attack Vector
The attack vector is network-based. An attacker who can reach the router's HTTP management port crafts a request targeting the formSetDebugCfg endpoint with an oversized payload in one or more of the vulnerable parameters. The malformed request triggers the overflow and crashes the web service. If the management interface is exposed to the wider network or the internet, the device becomes reachable by remote unauthenticated attackers.
No verified exploit code beyond the referenced proof-of-concept repository has been published. See the linked references for technical details.
Detection Methods for CVE-2026-36798
Indicators of Compromise
- Unexpected restarts or watchdog resets of the Tenda G0 router
- HTTP POST or GET requests to /goform/setDebugCfg or similar formSetDebugCfg endpoints containing abnormally long enable, level, or module parameter values
- Loss of management plane availability while the data plane briefly continues operating
- Repeated connections to the router's management port from unfamiliar source addresses
Detection Strategies
- Inspect HTTP traffic destined for the router's management interface for parameter values exceeding expected configuration lengths
- Deploy network IDS signatures that match oversized enable, level, and module parameters in requests to Tenda administrative endpoints
- Correlate device uptime resets with preceding inbound HTTP traffic to the management interface
Monitoring Recommendations
- Forward router syslog and SNMP trap data to a centralized logging system and alert on unscheduled reboots
- Monitor for HTTP requests to the router web interface originating from non-administrative network segments
- Track availability of the management interface and the WAN uplink using active health checks
How to Mitigate CVE-2026-36798
Immediate Actions Required
- Restrict access to the Tenda G0 web management interface to trusted administrative hosts only
- Disable remote (WAN-side) management on the device until a vendor patch is applied
- Place the router behind network segmentation and an access control list that blocks untrusted sources from reaching the HTTP management port
- Inventory all Tenda G0 devices running firmware v15.11.0.5 and prioritize replacement or isolation
Patch Information
No vendor patch for CVE-2026-36798 has been published at the time of NVD publication. Monitor the Tenda security advisories page for firmware updates addressing the formSetDebugCfg stack overflow conditions. Apply firmware updates promptly once released.
Workarounds
- Block external access to the router's HTTP management port at upstream firewalls
- Restrict management access to a dedicated administrative VLAN
- Replace the affected device with a model that receives active security maintenance if a fix is not provided within an acceptable window
- Reboot the device to restore service after a suspected exploitation attempt, then review logs for additional indicators
# Example: restrict management interface access using iptables on an upstream gateway
iptables -A FORWARD -p tcp -d 192.0.2.1 --dport 80 -s 10.10.10.0/24 -j ACCEPT
iptables -A FORWARD -p tcp -d 192.0.2.1 --dport 80 -j DROP
Disclaimer: This content was generated using AI. While we strive for accuracy, please verify critical information with official sources.
